On a Collision Course: When Space Debris Becomes a Real Threat
Garbage is a big problem on Earth: humanity produces too much trash and makes too little effort to change. What’s more, the problem follows us wherever we go: as soon as we started exploring space, we began polluting it as well. The question is: when will this problem become big enough for us to do something about it?
It began in 1993, shortly after fall of the Soviet Union. The Russian Space Forceslaunched a military communications satellite, Kosmos-2251. Since the country was short on money, it could not afford reliable satellites, and in 1995, Kosmos-2251was deactivated. It remained in orbit as a 950-kilogram piece of space junk.
Another two years later, an American company, Iridium Communications, launched its new satellite called Iridium 33, which operated for 12 years until, on a frosty winter day, some 789 kilometers above Siberia, it met its destiny — Kosmos-2251.
The satellites collided at a speed of 11,700 meters per second and created at least 2,000 large pieces of space debris and several more thousands of small pieces. The event marked the very first time cosmic trash destroyed a working satellite.
What Is Space Junk, Exactly?
We are not alone in the universe: in fact, our planet’s orbit is crowded by millions of manmade pieces. There are spacecrafts leftovers, dead satellites, paint flakes, bits of insulation and who knows what else, all in a wide assortment of sizes — from millimeters to meters in diameter.
More than 20,000 pieces of junk larger than a softball are currently orbiting Earth, traveling at speeds of up to eight kilometers per second. Also in orbit are some 500,000 pieces of debris the size of a marble or larger. At these velocities, a collision with such a “marble” can cause the same damage as an anvil falling from the height of two storeys.
Typical space debris consists of spacecraft remains, dead satellites and insulation bits in an assortment of sizes — from millimeters to meters in diameter. Photo credit: Chinanews.com
There are millions of paint flakes and objects of a similar size, with energy equivalent to being hit by a bullet. NASA has had to replace a number of its spacecrafts’ windows after they were hit by paint flecks. Each year, the total number of space debris increases by five percent. With satellites launches doubling in the last 23 years, the amount of debris is likely to grow exponentially.
Dreadful Flakes, Deadly Softballs and Other Orbit Dangers
Space debris is characterized by two features: its utter uselessness and the danger it presents. Astronauts face this danger during spacewalks as their space suits are incapable of protecting them if they are hit by anything larger than one centimeter in diameter. The International Space Station (ISS) is protected by the Whipple shield to a degree: it cannot withstand the impact of large pieces of debris. Building a shield large enough to protect the ISS from space junk of all sizes is simply too difficult and too expensive.
Therefore, when the station cannot protect its inhabitants, it has to change its position, which takes money and days to complete. Still, the ISS does so several times a year to avoid collisions. When there is no time to move, astronauts hide in emergency shelters and hope for the best.
Cosmic garbage is dangerous to all satellites, spacecraft, rockets and even Earth itself, as pieces of space debris can literally fall from the sky. For instance, in 2007, the pilot of a plane carrying 270 passengers from Chile to New Zealand saw a part of a Russian satellite falling down and nearly hitting the plane.
On average, one satellite is destroyed by space debris each year. That may affect everyone who uses television, GPS receivers and mobile phones.
How to Clean Up This Mess
When a new piece of space debris is created, two outcomes are possible: it slows down, enters the Earth’s atmosphere and burns up, or it crashes into another object in space, producing more smaller particulates with orbits of their own. In other words, space trash creates more space trash.
There are few technologies that can help clean the orbit. The only one that has already been tested is the RemoveDEBRIS satellite that uses net-capture. In the fall of 2018, it was released from the ISS, deployed its net and caught two small target CubeSat satellites.
The RemoveDEBRIS satellite cost $18.5 million — rather expensive for removing several kilograms of space junk. The entire project is expected to cost $400 million: that is how much one needs to capture and de-orbit the eight-ton Envisat spacecraft, the biggest piece of orbital junk, so it can burn up in the atmosphere. Envisat has been operated by the European Space Agency (ESA) since 2002. The ESA lost contact with the satellite in 2012, but Envisat is still in Low Earth Orbit (LEO). RemoveDEBRIS was funded in equal parts by the European Commission and by a consortium of 10 companies, including Airbus.
Trash collection methods aside, there are also some laser-based options. China has been researching space debris laser mitigation for a long time. The latest paper on this matter claims that a space-based pulsed laser station will be the most promising approach. It has “advantages such as simple operation, short response time, low cost, repeated use, and capable of both monitor and track activities,” says the paper.
Chinese scientists, however, did not specify the costs of this method. According to scientist Jialin Wen, the cost of every year of operation of a ground-based laser removal will be almost $87.9 million. That amount might seem large, but it is much cheaper than the net-capture method, which costs $5 million for each piece of space debris removed.
“Since the net-capture method is a kind of suicide removal and every satellite could only bring one space debris, when using the net-capture method, no matter what size the debris is, the cost stays at $5,04 million,” Wen concluded.
Russian researches are also working on laser technologies. They teamed up with Italian, French and Japanese scientists to construct a laser cannon that can be installed on the ISS. But this project is in its nascency now.
Canadian scientists offered to use a large cupola device to remove small- to medium-sized debris. The device will capture small pieces and slow down medium-sized ones, thus accelerating their destruction in the atmosphere.
“Current efforts in active debris removal strategies and mission planning focus on removing the largest, most massive debris. It can be argued, however, that small untrackable debris, specifically those smaller than five centimeters in size, also pose a serious threat,” researches from Laval University and McGill University noted.
How to Find the Money to Clean Up This Mess
Russia, United States and China are the top three space debris contributors by a wide margin. Since the beginning of cosmic era, Russia has left nearly 6,600 trackable junk objects in orbit. The US is responsible for more than 6,300 trackable pieces, and China — for more than 4,000 objects. By comparison, France, which is in the fourth place, produced only 554 trackable objects.
What’s worse, there are many little pieces: hundreds of thousands of them. Objects that are smaller than 10 centimeters cannot be detected, and a five-centimeter object can destroy a rocket or a satellite.
“The greatest risk to space missions comes from non-trackable debris,” said Nicholas Johnson, NASA’s chief scientist for orbital debris. According to the NASA Commercial Crew Program analysis, “the probability of on-orbit debris damaging the vehicle has the greatest effect on a loss of crew value.”
But even with so much junk in orbit, there have been surprisingly few disastrous collisions. That might be the reason why space agencies do so little to clean up, and instead focus their efforts on avoiding space trash.
“Everyone agrees that active debris removal is necessary, but they don’t have agreement on the urgency — when they should get started,” saidDarren McKnight of Integrity Applications Incorporated, a US engineering and software company.
“We’re humans. It’s the same story as with climate change. Until you’re hit personally, you don’t believe it,” said Luisa Innocenti, who heads the European Space Agency’s Clean Space program.
Basically, the only way to get government space agencies to clean after themselves and stop littering in space is to wait until the space debris problem become so big that not solving it will cost more than solving it. The “good” news is that, according to the Kessler Syndrome, it should not take long.
Evgenia Sokolovskaya
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